Car Radar System Key To Wingtip Protection

Honeywell has successfully tested a radar technology for low-cost solutions to the costly problem of “ramp rash,” the collisions between aircraft wings or other parts with other aircraft, vehicles or obstacles.

While the avionics company has not publicly divulged any new products, details of ground anti-collision systems have emerged in several recent patent applications and a 2012 request the company made to the Federal Communications Commission (FCC) to clarify or change its rules on the use of unlicensed radar in the 76-77-GHz band. The FCC allows automobile manufacturers to use the band for front-, side- and rear-facing “field disturbance monitors,” or millimeter-wave radars, for cars, but the technology is prohibited for use by aircraft on the ground or in the air. The FCC also allows the technology to be used for stationary foreign object debris (FOD) radars at airports.

In a December 2012 letter to the FCC, Honeywell requested that the agency review the rules to allow aircraft on the ground to use the technology. This followed on-aircraft tests made possible by an experimental license from the FCC, tests the company says confirmed the feasibility of using automobile-type radar co-located with wingtip navigation lights to detect obstructions and intruders. Honeywell demonstrated the project to airframers and airlines, which, given the magnitude of wingtip collision problems, are very interested in the technology, depending on the price. For Honeywell, the possibility of using a mass-produced sensor would help lower the costs for such a system compared to other types of radar, including pulsed and phased array.

“Wingtip collisions are a priority issue because of the enormous impact they have on air traffic operations and the frequency of such occurrences,” Honeywell wrote in the FCC letter. The Flight Safety Foundation in 2012 quantified the extent of the problem: Ramp accidents occur at a rate of one per 1,000 departures and cost the global airline industry $10 billion annually, including direct costs from damage as well as indirect costs from aircraft being out of service, public image problems and incident investigations.

The most recent high-profile ramp accident involved a British Airways747-400 that ripped through the second story of a brick building at South Africa's Tambo Airport last Dec. 22. Other recent events include an Air FranceA380 clipping the tail of a Comair BombardierCRJ700 at New York's John F. Kennedy International Airport in April 2011; an Airbus A380 demonstrator striking a building while trying to park at the Paris air show in June 2011; and an Eva Air Boeing 747 freighter's wing hitting an American Eagle ERJ140 at Chicago O'Hare International Airport in May 2012.

Following the O'Hare accident, the NTSB recommended that the FAA require manufacturers to install an anti-collision aid “such as a camera system” on all factory-built large aircraft “and other models where the wingtips are not easily visible from the cockpit to provide a cockpit indication that will help pilots determine wingtip clearance and path during taxi.” The recommendation noted that since 1993 the NTSB had investigated 12 accidents that occurred during taxi, when a large airplane's wingtips collided with another airplane or object on the taxiway.

The FAA responded that while a camera system may provide “a small benefit” at very low speeds, the two-dimensional image and limited field of view “make it unlikely that wingtip cameras would provide a measurable reduction in wingtip collision incidents at normal taxi speeds.” It also asserted that the benefits would not “justify the cost burden of an FAA mandate.” The NTSB, which had asked for a broader look at technologies other than camera systems, closed the recommendation in July but with a status of “Unacceptable Action.”

Honeywell's comprehensive approach to solving the problem using radar is detailed in part in several patent applications published Dec. 5, one by four engineers, including the enhanced ground proximity warning system's (EGPWS) creator, Don Bateman; and another by Honeywell Aerospace's senior chief engineer for human factors, Ratan Khatwa, and a second author. The wingtip protection system described in the FCC documents could be a simpler implementation of the system, however.

The Bateman patent describes an airport surface collision avoidance system that detects and tracks “intruders,” evaluates and prioritizes threats to the wing, tail, engine nacelles or other parts of the aircraft; declares and determines actions; and issues alerts to pilots or ground personnel (tugs, baggage carts, fuel trucks, wing walkers and others). The alerts are transmitted via wireless connection from antennas located in the navigation light pods. The system would help pilots steer clear of buildings and obstacles, including other vehicles and aircraft, during all visual conditions.

Detection is carried out using a radar sensor placed in the existing navigation light fixtures in each wingtip and at the top of the vertical stabilizer, although Honeywell says passive optical or acoustic sensors are also possible.

In the cockpit, the pilot would potentially receive three types of alerts or warning information: visual, audible and tactile. The visual alert would be displayed on an electronic flight bag (EFB) or cockpit display, perhaps showing the aircraft wingtips outlined or a highlight of the obstruction. An aural alert could be a beeping sound from the existing EGPWS that increases in frequency as the obstacle gets closer, changing into a continuous tone for a warning, or possibly a voice alert of “Left” or “Right” to direct the pilots' attention to an obstruction. The information would also be sent via wireless transmitter in the navigation light module to alert ground crews to the threat, too.

The Khatwa patent relates more to displaying such information, and includes description of a top-down image of an aircraft on an EFB or flight display, with visual range rings at selectable values extending from both wingtips. Bateman notes that the sensor range will depend on time available to detect an intruder, evaluate and prioritize threats, and to declare and determine actions for the pilot or ground crews to take.

One notional display would show the primary targets (those located between each wingtip and the fuselage) as larger solid circles, and secondary targets (those outboard of the wingtip) as hollow circles. The system could also display the relative height of the obstacle, to show whether the aircraft wing or other part could safely taxi over or under it.

Honeywell tells the FCC in its request that the prototype wingtip collision system would meet all existing requirements for automobile radar and would be able to “share the band” with FOD radar. While the company continues to work with the FCC on the request, it is holding off on additional engineering and human factors developmental tasks pending the agency's approval to use the spectrum for ground-based aircraft.